The design and execution of reliable complexity enhancing chemical transformations continues to be a goal at the forefront of synthesis. Since transition metal catalysts increase efficiency and enable new routes to complex molecules, their utility will continue to grow. This proposal outlines a research plan for developing a broad class of metal catalyzed reactions that utilize the electrophilic ring closure of 1,5- and 1,6-dienes, to generate cationic intermediates capable of participating in and initiating a wide range of reactions. The products of metal catalysis are unique in that they are under CATALYST CONTROL, which enables the transformations to be made with control of enantioselectivity, regioselectivity, and skeletal connectivity. In contrast to purely ionic means to cationic chemistry, a significantly greater degree of reaction control can be exercised. SPECIFIC AIMS (1) To develop a palladium-catalyzed reaction that cyclo-generates reactive "cations" from 1,5- and 1,6-dienes for subsequent trapping, rearrangement, and ring-annulat!ve cation-olefin reactions. (2) To develop pincer- and pseudo-pincer electrophilic catalysts for polyene activation/cation generation and cycloisomerization catalysis. (3) To develop intermolecular C-C bond forming reactions that generate trappable intermediate cations for cascade reactions (e.g. Prins reaction).